A method for suppressing the generation of transient phenomena, which impact electric power systems and electric power equipment, by controlling the opening or closing timing of a circuit breaker for power, has been proposed (e.g. see Non-patent Document 1).
A specific invention to implement this method for suppressing the generation of transient phenomena, which has already been proposed, is a switching controlgear of circuit breaker which switches a circuit breaker contact at a timing between a current zero point and a peak value of the circuit breaker current when current is interrupted, and controls the closing timing of the circuit breaker contact according to the type of load when the circuit breaker contact is closed (e.g. see Patent Document 1).
Such a switching controlgear of circuit breaker has already been used in many actual electric stations (see Non-patent Document 1).
All of the switching controlgear of circuit breakers according to Patent Document 1 have a function to delay the output timing of an opening command signal or closing command signal to the circuit breaker, so that the circuit breaker can interrupt or not interrupt at a predetermined phase when the opening command signal or closing command signal is detected. Such a switching control for a circuit breaker is called “synchronous opening control” or “synchronous closing control”.
Patent Document 1: Japanese Patent Application Laid-Open No. H3-156820
Non-patent Document 1: Catalogue publication 1HSM 9543 22-01en, Controlled Switching Buyer's Guide Edition 1, 2004-05, ABB Power Technologies
Many of the switching controlgear of circuit breakers applied to electric stations have a means for connecting with external equipment, such as a personal computer (hereafter PC), and has a function to acquire various data, including main circuit current waveforms and power system voltage waveforms when the switching control of the circuit breaker is performed.
In order to connect the synchronous switching control device of a circuit breaker and an external equipment, such as a PC, however, dedicated communication software and maintenance software must be installed on the PC in advance.
In the case of the switching controlgear of circuit breaker shown in Non-patent Document 1, for example, dedicated communication software and maintenance software are provided to the user via CD-ROM. In this case, the user must install the dedicated software written on the CD-ROM on a PC using a CD-ROM driver. Therefore the PC, in which the dedicated software is not installed, cannot be connected to the switching controlgear of circuit breaker, which is inconvenient, especially in terms of storing and managing various acquired data. Also in the switching controlgear of circuit breaker shown in Non-patent Document 1, a serial communication standard cable, RS-232C, is used to connect with a PC, and the maximum length of the RS-232C cable is about 15 m.
Therefore in the case of the switching controlgear of circuit breaker shown in Non-patent Document 1, connection with a PC is normally a local connection at the work site, which is not convenient for remote control. If remote control is required, [the switching controlgear of circuit breaker] must be connected using a modem via a telephone line, for example, instead of an RS-232C cable, which is not only inconvenient but also has a slow communication speed and poor work efficiency.
Also only one switching controlgear of circuit breaker can be connected to one PC at a time, which means that a switching operation is required to perform maintenance and various data collection for the switching controlgear of circuit breakers installed in a plurality of circuits, which has poor work efficiency.